Claw-tooth rotor dynamoelectric machine

ABSTRACT

A synchronous machine having a Lundell-type rotor is provided with a stationary excitation winding positioned at the axial end of the rotor with a continuous annular magnetic flux collector core surrounding the winding. This collector provides a dual, relatively shorter, continuous flux path between alternate poles of the rotor as it sweeps past the flux collector without including the stator yoke or housing in the flux path.

United States Patent 51 3,663,846 Wagner et al. May 16, 1972 [54]CLAW.TOOTH ROTOR 2322259 85192; gowlers "310/263 x ,3 l, 52 5 19 pel0/263X DYNAMOELECTRIC MACHINE 3,452,228 6/1969 Woolley .310/263 xInventors: Paul D. Wagner, 549 Ludlow Ave., Cincinnati, Ohio 45220; JohnJ. Keuper, 7 Alanna Drive, Cold Springs, Ky. 41076 Filed: June 7, 1971Appl. No.: 150,685

References Cited UNITED STATES PATENTS 8/1897 Rice ..3 10/168 PrimaryExaminerD. F. Duggan Attorney-John P. Hines, Robert B. Benson and Lee H.Kaiser 5 ABSTRACT A synchronous machine having a Lundell-type rotor isprovided with a stationary excitation winding positioned at the axialend of the rotor with a continuous annular magnetic flux collector coresurrounding the winding. This collector provides a dual, relativelyshorter, continuous flux path between alternate poles of the rotor as itsweeps past the flux collector without including the stator yoke orhousing in the flux path.

2 Claims, 2 Drawing Figures Patented May 16, 1972 CLAW-TOOTH ROTORDYNAMOELECTRIC MACHINE This invention pertains in general todynamoelectric machines and more particularly to a synchronousdynamoelectric machine having a Lundell-type rotor and a stationaryexcitation winding.

A synchronous Lundell-type machine has the advantage of being able tooperate at high speeds because of the absence of conventional windingson the rotor. Additionally, the absence of rotating excitation windingsobviates the necessity of providing slip rings, brushes, or permanentmagnets. Such machines have, however, been relatively expensive tomanufacture. One reason for this added expense is because the statoryoke and/or housing provide a portion of the magnetic flux path for themachine. This requires that the yoke and/or housing be constructed of amore expensive, permeable material.

It is the general object of this invention to provide aLundell-typedynamoelectric machine of more simplified and inexpensiveconstruction.

An additional object of the subject invention is to provide asynchronous Lundell-type machine having a fixed non-pulsating level ofexcitation current.

A further object of the invention is to provide a machine of the aboveidentified type with a dual, relatively shorter, and therefore moreefficient, flux path.

A more specific object of the subject invention is to provide a machineof the above identified type wherein neither the stator housing nor yokeis included in the magnetic flux path.

These and other objects of the subject invention will become more fullyapparent as the following description is read in light of the attacheddrawing wherein:

FIG. 1 is a longitudinal sectional view of a part of a dynamoelectricmachine constructed in accordance with the invention; and

FIG. 2 is a perspective view of the rotor of the subject dynamoelectricmachine.

The description of this machine will, for the purposes of clarity, bemade in connection with an electric motor. However, it should beunderstood that it is not intended to so limit the invention which hasapplication to all, dynamoelectric machines.

Reference is made herein to a Lundell-type machine. It is believed thatsuch a machine is sufficiently well known to those skilled in the art towhich this invention pertains that a description is not necessary.However, if necessary, reference is made to US. Pat. No. 3,321,652.

Referring to the attached drawing, in particular FIG. 2, the rotorgenerally designated 6 is constructed of two magnetic sections 7 and 8.The rotor sections are connected to a nonmagnetic motor shaft 9 in anyconventional manner.

The rotor sections 7 and 8 each include angularly spaced finger pairs 11and 12, respectively. The fingers of each pair are disposed axially andare interleaved in the manner shown in FIG. 2. The number of fingers 11and 12 of each rotor section is optional and corresponds to the numberof pole pairs of the machine. The machine shown for purposes ofillustration is a four-pole machine. The two rotor sections 7 and 8 areconstructed of material of good magnetic permeability, such as steel,and they are magnetically isolated from one another by a nonmagneticfiller material 13 such as, for instance, aluminum.

Referring now more particularly to FIG. 1, conventional statorlaminations l4 and winding 16 are positioned about the rotor 6 in theconventional manner.

Stationary excitation windings 17 are positioned on opposite axial endsof the rotor 6 symmetrical with the rotor shaft. Each excitation winding17 is surrounded by a collector core 18. Each collector core 18 isprovided with a pair of legs 19 and 21 which extend toward the rotorsections. The legs 19 of the collector cores 18 provide an air gap 22with the fingers 11 and 12 of the rotor sections. The legs 21 of thecollector cores 18 provide an air gap 23 with the bases 24 and 26 of therotor sections 7 and 8.

These air gaps 22 and 23, together with the air gap 27 betweenthe statorlaminations l4 and the outer peripheral surface of the rotor, provide adual magnetic flux path for the machine. The flux path is from the leg19 across the air gap 22 into the finger ll of rotor section 7 acrossthe air gap 27 into the stator laminations, back across the air gap 27into the adjacent rotor section 8. From here flux flows over two paths:across both right and left air gaps 22 and 23 into legs 19 and 21,respectively, of the collector cores 18.

With the arrangement above described it can be seen that a lessexpensive, more simplified, excited synchronous dynamoelectric machinehas been defined. With this arrangement, even though the fingers 11 and12 and the bases 24 and 26 present a variable reluctance to the excitingcoils 17, these variations disappear as the fingers sweep past thecontinuous surface of the stationary collectors 18. With thisarrangement no flux or voltage pulsation occurs, and a fixednonpulsating level of excitation current is achieved. Furthermore, theyoke and housing of the machine are not a part of the flux path and,therefore, may be made of low cost materials normally used inconventional induction motors, such as cast iron or aluminum.

We claim:

1. A dynamoelectric machine comprising: a stator means of magneticmaterial; rotor means journaled for rotation within said stator meansand defining a flux-traversing air gap therewith, said rotor including aplurality of sections magnetically isolated from one another with eachhaving an annular base portion and a finger portion of magneticmaterial, said finger portions projecting axially toward each other andspaced angularly from one another and defining poles for cooperationwith said stator means, each of said fingers terminating axially beyondthe end of the base portion of the other section; and a stationaryfield-producing means including a coil portion and a core portion ofmagnetic material positioned at the axial end of said rotor means, saidcore portion having a pair of spaced legs, one of said legs forming afluxtraversing air gap with the base portion of one of said rotorsections and the other leg forming a flux-traversing air gap with thefinger of the other of said rotor sections.

2. The dynamoelectric machine set forth in claim 1 wherein saidstationary core surrounds said stationary coil.

1. A dynamoelectric machine comprising: a stator means of magneticmaterial; rotor means journaled for rotation within said stator meansand defining a flux-traversing air gap therewith, said rotor including aplurality of sections magnetically isolated from one another with eachhaving an annular base portion and a finger portion of magneticmaterial, said finger portions projecting axially toward each other andspaced angularly from one another and defining poles for cooperationwith said stator means, each of said fingers terminating axially beyondthe end of the base portion of the other section; and a stationaryfield-producing means including a coil portion and a core portion ofmagnetic material positioned at the axial end of said rotor means, saidcore portion having a pair of spaced legs, one of said legs forming aflux-traversing air gap with the base portion of one of said rotorsections and the other leg forming a flux-traversing air gap with thefinger of the other of said rotor sections.
 2. The dynamoelectricmachine set forth in claim 1 wherein said stationary core surrounds saidstationary coil.